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On 06/22/2017 01:20 PM, Benjamin Gaignard wrote: > 2017-06-20 19:31 GMT+02:00 Eric Anholt <eric@anholt.net>: >> Archit Taneja <architt@codeaurora.org> writes: >> >>> On 06/16/2017 08:13 PM, Eric Anholt wrote: >>>> Archit Taneja <architt@codeaurora.org> writes: >>>> >>>>> On 06/16/2017 02:11 AM, Eric Anholt wrote: >>>>>> If the panel-bridge is being set up after the drm_mode_config_reset(), >>>>>> then the connector's state would never get initialized, and we'd >>>>>> dereference the NULL in the hotplug path. We also need to register >>>>>> the connector, so that userspace can get at it. >>>>>> >>>>> >>>>> Shouldn't the KMS driver make sure the panel-bridge is set up before >>>>> drm_mode_config_reset? Is it the case when we're inserting the >>>>> panel-bridge driver as a module? >>>>> >>>>> >>>>> All the connectors that have been added are registered automatically >>>>> when drm_dev_register() is called by the KMS driver. Registering a >>>>> connector in the middle of setting up our driver is prone to race >>>>> conditions if the userspace decides to use them immediately. >>>> >>>> Yeah, this is fixing initializing panel_bridge at DSI host_attach time, >>>> which in the case of a panel module that creates the DSI device >>>> (adv7533-style, like you said I should use as a reference) will be after >>>> drm_mode_config_reset() and drm_dev_register(). >>> >>> Okay. In the case of the msm kms driver, we defer probe until the >>> adv7533 module is inserted, only then we proceed to drm_mode_config_reset() >>> and drm_dev_register(). I assumed this was the general practice followed by >>> most kms drivers. I.,e the kms driver defers probe until all connector >>> related modules are inserted, and only then proceed to create a drm device. >> >> The problem, though, is the panel driver needs the MIPI DSI host to >> exist to call mipi_dsi_device_register_full() during the probe process. >> The adv7533 driver gets around this by registering the DSI device in the >> bridge attach step, but drm_panel doesn't have an attach step.
I'm not sure how we can get around this. We had discussion about this on irc recently, but couldn't come up with a good conclusion. We could come up with a panel_attach() callback to make it similar to bridges, but that's just us avoiding the real issue.
>> >> Another alternative is my original version of the panel driver that was >> a mipi_dsi_device driver that registered the panel during the DSI device >> probe. That's why vc4's panel lookup is during the MIPI DSI attach >> phase, currently. >
This would require you to have a DSI device node in DT, rather than an i2c node, right? I don't know if we should do that because of a limitation in our drm_mipi_dsi and drm_panel frameworks.
Does anyone have better ideas?
Thanks, Archit
> + Philippe in copy because we have the same probing issue when adding > panel-bridge > with the dsi bridge > >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/dri-devel >>
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